1. Field of the Invention
The present invention relates to an image calibration method and an image processing system using the method, and more particularly, to an image calibration method that does not use pixels in the same row as reference pixels, and an image processing using the method.
2. Description of the Prior Art
An image processing system has an image sensor (e.g., a charge-coupled device, a CCD) for sensing incident light from a target object and converting the incident light into electric charges. FIG. 1 is a block diagram of a conventional image sensor 100. As shown in FIG. 1, the image sensor 100 includes a pixel array 101 and a row sensor 103. The pixel array 101 usually includes an effective pixel area 105 and an original shading region 107. However, some other image sensors may further include a reference shading region 108. The row sensor 103 is implemented for sensing pixels of the effective pixel region 105, and the sensing manner thereof senses all pixels at the same sensing row at once, for example, all pixels within a sensing row 109 or 100, and then outputs sensed pixel values one by one. Reference pixel regions (called black pixel regions) 111 and 112 are for calibrating sensed pixel values within the sensing rows 109 and 110, respectively. This is because there may be background noise within each image, and sensing pixel values of the reference shading region 108 helps to acquire the background noise and thereby derive a calibration value. Next, the calibration value is used to calibrate pixel values to be outputted. For example, an outputted pixel value is derived from a pixel value within the sensing row 109 or 100 minus the calibration value.
However, this kind of mechanism is only available for calibrating the sensed row having a reference shading region located within the same sensed row, resulting in an inflexible circuit design.